Re: How do small animals such as the temperate North American squirrel survive?

Dear Cerulean,
Your squirrels in the Arctic are ground squirrels . They have a completely
different lifestyle underground, as opposed to the arboreal squirrels we
know. The ecology of arboreal squirrels depends on the individual  species
but basically the competition is fierce. They may even be killed and eaten
by their own species, although inter-specific competition is suspected in
American grey populations in Europe and the native red squirrel. (This is a
whole different ball-game, where battle has raged for generations between
the grey squirrel virus faction and the more physical competitive ideas of
competition). 
However, I’m afraid your answer needs no species details unless you would
like to compare the Eastern and western American grey squirrels(and a red)
or the Canadian ground squirrels or gophers with their Asian brothers (same
species, known as sousliks). In all events, the gopher lives below -30o
(down to -40oC) and is the best known mammal to super-cool or allow its
body to lower its temperature below freezing!  Hibernation among mammals is
common, but this is really special as ice can’t be allowed to form in the
fluid bloodstream. Basically the tundra habitat  demands the ground
squirrel chooses a deep sandy burrow where it can spend most of the year
sheltered from extreme temperatures. This has helped it to evolve the
extreme features it needs for survival.
If you want to compare arboreal squirrels, their “drey” is usually formed
in the branch of a tree in Summer and within a hollow of a tree in winter.
Temperatures in forests never sink as low(or rise as high) as exposed
ground, as you’ll soon find if you notice cold exposed hillsides in Winter
or cool woods in mid-Summer. They may die if their stores of food run out
or maybe they just got old---.
Good luck with your mammal studies in future. Hopefully we can help you
more with questions for which we can define your answer more closely or
advise you on local fauna that you can really enjoy observing. As far as
these cold wildernesses are concerned, you could be grateful that you don’t
have to survive for ten months of the year , asleep in an igloo!